DESCRIPTION: (Applicant's Abstract) As we enter the 21 st century, the United States is faced with a problem that has plagued the world for thousands of years. Syphilis remains an important public health problem nearly fifty years after the introduction of penicillin. The proposed new study, called The Epidemiology and Outcome of Syphilis in Drug Users, will be conducted in the urban heartland of America in a city that has been experiencing a syphilis epidemic since 1991. The investigators will study the relationship between drug use and syphilis by evaluating syphilis serology and interview data from 2,200 drug users involved in three separate NIDA- sponsored longitudinal projects to accomplish the following aims: The Epidemiologic Aims include: a) determining the critical risk factors for syphilis and describing the proportion of drug users who develop syphilis; b) evaluating whether drug users in treatment are less likely to develop syphilis; c) evaluating the validity of self-reported information on syphilis compared to serologic testing; d) evaluating whether a syphilis epidemic increases the proportion of drug users who develop HIV infection in an area of low prevalence of HIV infection among drug users. The Health Services/Outcome Aims include: a) evaluating the strategies used to treat and control syphilis in drug users; b) providing data on the site of care for the diagnosis and treatment of syphilis and other STDs; c) determining the adequacy of syphilis follow up in drug users; d) describing how access or barriers to medical care affects the management of syphilis in drug users; e) evaluating the knowledge and practice patterns of health care providers most likely to be involved in the treatment of persons with sexually transmitted diseases; f) determining the cost-effectiveness of syphilis control efforts. To accomplish these aims the investigators will: a) utilize the existing analogous data and stored blood specimens from three NIDA-funded studies; b) test the stored specimens for syphilis and combine this with ongoing syphilis testing in one of the "parent" studies; c) obtain information on study participants and syphilis control efforts from the health department; d) conduct a proportionate survey of 100 health providers. Thus, the major goals of this study are to identify the specific factors associated with the development of syphilis in drug users and evaluate the efforts of health care providers and the public health establishment to provide services to treat and control syphilis in an effort to develop more effective interventions to reduce the occurrence of syphilis.